QCD β Function with Two Flavors of Dynamical Wilson Fermions

We test the asymptotic scaling behaviour of state-of-the-art simulations of QCD with two flavors of light Wilson fermions. This is done by matching π and ρ masses on lattices of size 16 × 32 and 8 × 16. We find that at β = 6/g = 5.3 matching is not possible over a range extending down to β = 3.5. The large lattice data at β = 5.5 matches the small lattice values at β = 4.9(1) leading to a shift ∆β = 0.6(1), considerably larger than the perturbative prediction of 0.45. In both cases we conclude that the simulations are very far from the asymptotic scaling region.